Installation guide

Chapter 21. Online Storage Management
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interconnect scanning is not recommended if free memory is less than 5% of the total memory in
more than 10 samples per 100. It is also not recommended if swapping is active (non-zero si and
so columns in the vmstat output). The command free can also display the total memory.
The following commands can be used to scan storage interconnects.
echo "1" > /sys/class/fc_host/host/issue_lip
This operation performs a Loop Initialization Protocol (LIP) and then scans the interconnect
and causes the SCSI layer to be updated to reflect the devices currently on the bus. A LIP is,
essentially, a bus reset, and will cause device addition and removal. This procedure is necessary
to configure a new SCSI target on a Fibre Channel interconnect.
Bear in mind that issue_lip is an asynchronous operation. The command may complete before
the entire scan has completed. You must monitor /var/log/messages to determine when it is
done.
The lpfc and qla2xxx drivers support issue_lip. For more information about the API
capabilities supported by each driver in Red Hat Enterprise Linux, refer to Table 21.1, “Fibre-
Channel API Capabilities”.
/usr/bin/rescan-scsi-bus.sh
This script was included as of Red Hat Enterprise Linux 5.4. By default, this script scans all the
SCSI buses on the system, updating the SCSI layer to reflect new devices on the bus. The script
provides additional options to allow device removal and the issuing of LIPs. For more information
about this script (including known issues), refer to Section 21.15, “Adding/Removing a Logical Unit
Through rescan-scsi-bus.sh”.
echo "- - -" > /sys/class/scsi_host/hosth/scan
This is the same command described in Section 21.6, “Adding a Storage Device or Path” to add
a storage device or path. In this case, however, the channel number, SCSI target ID, and LUN
values are replaced by wildcards. Any combination of identifiers and wildcards is allowed, allowing
you to make the command as specific or broad as needed. This procedure will add LUNs, but not
remove them.
rmmod driver-name or modprobe driver-name
These commands completely re-initialize the state of all interconnects controlled by the driver.
Although this is extreme, it may be appropriate in some situations. This may be used, for example,
to re-start the driver with a different module parameter value.
21.10. iSCSI Discovery Configuration
The default iSCSI configuration file is /etc/iscsi/iscsid.conf. This file contains iSCSI settings
used by iscsid and iscsiadm.
During target discovery, the iscsiadm tool uses the settings in /etc/iscsi/iscsid.conf to
create two types of records:
Node records in /var/lib/iscsi/nodes
When logging into a target, iscsiadm uses the settings in this file.
Discovery records in /var/lib/iscsi/discovery_type
When performing discovery to the same destination, iscsiadm uses the settings in this file.
Before using different settings for discovery, delete the current discovery records (i.e. /var/lib/
iscsi/discovery_type) first. To do this, use the following command: